Microstructural changes in TlBa/sub 2/CaCu/sub 2/O/sub 7-/spl part// thin films after reducing anneals which enhance critical current density

Microstructural changes in TlBa/sub 2/CaCu/sub 2/O/sub 7-/spl part// (Tl-1212) epitaxial thin films resulting from low oxygen partial pressure furnace anneals at 600/spl deg/C are studied using high resolution transmission electron microscopy (TEM). These post-growth anneals have been shown to significantly raise the superconducting transition temperature from 70 to 90 K, and greatly improve the magnetic flux pinning and the critical current density. Changes occur in both the microstructure and the morphology of the films that correlate with changes in J/sub c/. Plan view TEM and high-resolution cross-sectional TEM analysis of the films before and after anneals demonstrates changes in the lattice fringe image, overall contrast modulation, and nanometer-scale discontinuities.